The present invention relates to a head depression type dispenser which is capable of being mounted on a container via a cap for drawing liquid in the container into a cylinder and pressurizing and dispensing the liquid by the movement of a piston in the cylinder, the piston movement being produced by the depression of a head thereof.
In a conventional dispenser of this type, a piston is mounted in a head, a cylinder is mounted in a cap, and the dispenser is mounted on a container via the cap. This dispenser is constructed to lower the piston together with the head by depressing the head, for example, in a downward direction, thereby dispensing liquid contained in the container. In other words, when the head is depressed, the piston descends in the cylinder, thereby dispensing the liquid in the container. A conventional head depression type dispenser generally includes a head, a cap, a piston mounted in the head, a cylinder mounted in the cap, primary and secondary valves for controlling the inflow and outflow of liquid in the cylinder, a return spring for biasing the piston, and a secondary valve spring for pressing the secondary valve to a valve seat. Thus, the conventional head depression type dispenser includes at least eight components. If the number of components can be reduced, it will not only decrease the manufacturing cost of the respective components but will simplify the assembling of the dispenser, thereby making the production of the dispenser inexpensive. For that purpose, various modifications have been applied to the conventional dispenser so as to reduce the number of its components. However, a head depression type dispenser which largely reduces the number of components has not yet been proposed.
On the other hand, there is disclosed in U.S. Pat. No. 3,749,290 issued on July 31, 1973 to L. A. Micallef, not a head depression type but a trigger type sprayer in which a cylinder is formed of any one of many available moldable flexible materials of either synthetic or natural resin or plastic. In this conventional sprayer, the upper end of a cylinder is engaged by the elasticity thereof with the outer surface of a lip formed on a sprayer body, thereby securing a liquid seal between the cylinder and the sprayer body to form a secondary valve. Accordingly, this sprayer does not have a secondary valve as an independent member. Futher, the elasticity of the cylinder itself serves as a secondary valve spring, thereby eliminating the secondary valve spring. The side of the cylinder is elastically pushed inward by an operating arm formed integrally with a trigger so as to pressurize the liquid in the cylinder. Further, negative pressure is produced in the cylinder by isolating the operating arm from the side of the cylinder to return the cylinder to the original shape, thereby sucking the liquid into the cylinder. Since the liquid is pressurized and sucked by the partial deformation of the cylinder, a piston is unnecessary, and a return spring for the piston is also unnecessary. Thus, in Micallef's sprayer, the piston, secondary valve, return spring for the piston and valve spring for secondary valve can be omitted. Since this sprayer, however, urges the operating arm to the side of the cylinder, the cylinder is elastically pushed only partly at the side, with the result that the liquid in the cylinder cannot be sufficiently pressurized. Further, since partial deformation occurs, the cylinder is accordingly damaged.
A head depression type dispenser in which the cylinder is formed of flexible material has not yet been proposed. Paricularly, the dispenser of this type should be necessarily packaged and conveyed in such a way as to prevent the depression of its head before initiating use of the dispenser. It is further necessary in the dispenser of this type to prevent the out-flow of liquid by the depression of its head due to careless movement or overturning when it is displayed in a shop. In other words, a so-called virgin lock is required to prevent the unnecessary or careless depression of its head before intentional use of the dispenser. It is also necessary to provide a locking means for protecting the dispenser against the depression of its head at a non-use time, even after the starting of use of the dispenser, so as to protect a child against an accident, making it "childproof". It has been desired to reduce the number of components of the conventional head depression type dispenser due to the necessity of such a virgin lock and childproofing, but on the contrary, there has been a trend toward increasing the number of components, thereby causing an increase in the production cost of the head depression type dispenser.